Hot water supply system



N v- ,1 67 J. T. MULLER ETAL v3,353,530

HOT WATER SUPPLY SYSTEM April 8. 1966 System Demand INVENTORS JOHN T.MULLER EDGAR D. HODGSONJR BERNARD H.8REMER Condensat FIG. 1

3,353,530 HOT WATER SUPPLY SYSTEM John T. Muller, Nutley, N.J., Edgar D.Hodgson, Jr., Salt Lake City, Utah, and Bernard H. Bremer, Allendale,N.J., assignors to Leslie Co., Lyndhurst, N.J., a corporation of NewJersey Filed Apr. 8, 1966, Ser. No. 541,201 3 Claims. (Cl. 126-362) Thisinvention relates to hot water supply systems including a hot waterheater and a hot water storage tank and, more particularly, to animproved hot water supply system which permits the direct supplying ofhot water to the demand whenever the demand is within the capacity ofthe heater regardless of the temperature of the water in the storagetank.

In hot water heating systems it is conventional to provide for shortduration peak demands by augmenting the hot water from a limited heatercapacity with hot water which has been heated and stored in a relativelylarge storage tank. It is important in such systems to relate the demandtime to the storage capacity. Also, after a sustained peak demand, it isa common experience to have the storage tank filled with cold water sothat, for a period of time, only cold water is available to the systemfrom the storage tank.

We have now devised a circuit for a hot water supply system in which nowater is taken from the storage tank as long as the demand is Within theheaters capacity, in which the demand requirements above the heaterscapacity are handled jointly by the heater and the stor age tank, and inwhich excess heater capacity during periods of low demand or no demandis utilized to heat the water in the storage tank. The hot Water supplysystem of the present invention includes a hot water heater, a hot waterstorage tank, a cold water supply line having a branch communicatingwith the heater and another branch line communicating with the storagetank, and a hot water supply line having a branch line communicatingwith the heater and another branch line communicating with the storagetank. Pursuant to the invention, a spring-loaded check valve ispositioned in the cold water branch line to the storage tank andoperable to permit flow therethrough to the tank when the pressure inthe tank is reduced by the demand to a level representative of themaximum heating capacity flow rate of the heater, and a by-passreverse-flow circuit is connected across the spring-loaded check valvein the aforesaid cold water branch line. The by-pass circuit includes acirculating pump operable in response to a water temperature in thestorage tank below a predetermined storage temperature and furtherincludes a check valve disposed to permit flow from the pump through theby-pass line only in a direction opposite to the direction of flow ofcold water through the springloaded check valve. In particularlyadvantageous embodiment of the invention, a two-line parallel flowcircuit is positioned in the by-pass line with a fixed flowrate valve inone line and with a controllable flow rate valve in the other line. Acontrol element is further provided for the aforesaid controllableflow-rate valve responsive to a pressure drop in the hot water supplyline and adapted to close the valve when there is substantially nodemand'on the hot Water supply line.

These and other novel features of the hot water supply system of theinvention will be more readily understood from the following descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a hot water heating system embodyingthe invention; and

FIG. 2 is a schematic diagram of another embodiment of the invention ina hot water heating system.

' United States Patent Ofiiice 3,353,530 Patented Nov. 21, 1967 In thehot water heating system shown in FIG. 1, a cold water supply line 5 isprovided with two branch lines, one branch line 6 being connected to ahot water heater 7 and the other branch line 8 being connected to a hotwater storage tank 9. A hot water supply line 10 is connected by onebranch line 11 to the output of the heater 7 and by another branch line12 to the output side of the hot water storage tank 9. The hot waterheater 7 and the hot water storage tank 9 are thus connected in parallelbetween the cold water supply line 5 and the hot water supply line 10.

In order to limit the flow of hot Water from the storage tank 9 to thehot water supply line 10 only when the demand for hot water exceeds theheating capacity of the heater 7, the cold Water supply branch line 8 isprovided with a spring-loaded check valve 13 set so as to open only whenthe pressure drop in the hot water supply line, felt back to thedelivery side of the check valve 13, corresponds to a hot water demandrate in excess of the heating capacity flow-rate of the heater 7. Whenthe demand thus exceeds the capacity flow rate of the heater, thepressure drop across the check valve 13 is suflicient to open the valveand permit cold water to flow through the branch line 8 into the storagetank 9. Flow of water into the tank permits flow of hot water from thetank through the hot water branch line 12 to join the hot water flowingthrough the other hot Water branch line 11 to satisfy the demand in thehot water supply line 10.

When the demand in the hot water supply line 10 is not sufiicient toopen the check valve 13 and permit hot water to flow from the storagetank to join the output from the heater, provision is made for some ofthe hot water output from the heater to flow in the opposite directionthrough the hot water branch line 12 and into the storage tank. This isaccomplished by providing a by-pass line 14 across the spring-loadedcheck valve 13 arranged to effect fiow in a direction opposite to thatthrough the check valve 13. The by-pass line 14 contains a circulatingpump 15 and a check valve 16 which permits flow through the line 14 onlyin the aforementioned direction. Accordingly, when the spring-loadedcheck valve 13 is closed, the circulating pump draws water from thestorage tank 9 through the line 14 and I into the cold water branch line6 to the heater. This flow of water from the storage tank to the heateris accompanied by a corresponding flow of hot water into the storagetank from the heater through the lines 11 and 12. Thus, whenever thedemand for hot water is not at a peak level such as to open thespring-loaded check valve 13, some of the hot water output from theheater 7 will be diverted to the storage tank 9 regardless of whetherthere still exists a moderate demand or no r demand in the hot watersupply line 10. It is presently preferred to control the circulatingpump 15 with a temperature sensor 17 in the storage tank circulationline 14 so as to stop the circulation of hot water between the heater 7and the storage tank 9 when the temperature in the storage tank reachesa predetermined level. In addition, the heater 7 andthe hot water supplyline 10 can be provided with a feed-back sensor connection, shown as adotted line 18 in FIG. 1, pursuant to conventional heating systemsprovided with temperature regulations.

The modification of the heating system of the invention shown in FIG. 2differs from that shown in FIG. 1 in two respects: the heater circuitenclosed in the broken line 20 is substantially that described andclaimed in application Ser. No. 317,265, filed Oct. 18, 1963, now PatentNo. 3,232,336, and the hot water circulation line 14 is provided with atwo-line parallel flow circuit between the circulating pump 15 and thecheck valve 16. In the heater circuit enclosed by the broken line 20,the heater 7 comprises a heat exchanger supplied with steam through asteam control valve 21 and having a condensate outlet. The hot wateroutput from the heater 7 passes through a blending valve 22 in which thehot water is mixed with cold water from a bypass line 23 in proportionscontrolled by an element such as a differential diaphragm 24. Thediaphragm 24 is responsive to the difference in pressure between thecold water supply line 6 (through line 23) and the demand hot watersupply line (through line 11). Movement of the diaphragm 24 istransmitted through a mechanical linkage 25, for example, to theblending valve 22, and this movement of the linkage 25 is arranged todevelop a signal output from an interconnected conventional signalgenerating device 26. The output from this generator, which is thereforeproportional to the hot water demand, is transmitted through aconnection 27 to the steam control valve 21 so that steam is supplied tothe heat exchanger in proportion to the demand for hot water.

In the storage tank circulating line 24 in FIG. 2, the parallel fiowcircuit comprises two lines 23 and 29. One line, such as line 28, isprovided with a fixed flow-rate valve or orifice 39, and the other line29 is provided with a variable flow control valve 31. The two lines 28and 29 can be discrete lines as shown in FIG. 2 or the line 28 can beformed as an integral by-pass in the valve 31. The output of the signalgenerating device 26, which is connected to the steam supply valve 21 asaforementioned, is also advantageously connected to the variable flowcontrol valve 31 through a connection 32, so that maximum output fromthe generating device 26 closes the variable flow control valve 31.Alternatively, the valve 31 can be a spring-loaded check valve such asvalve 13 in FIG. 1, in which case the spring-loaded diaphragm of thecheck valve, with its connections to opposite sides of the valve,provides the control element for controlling operation of the valve inresponse to a pressure drop in the hot water supply line.

In operation of the system shown in FIG. 1, a demand for hot water inthe hot water supply line 10 is met solely by hot water from the heater7 up to a rate equal to its heating capacity. When the demand exceedsthis capacity, the pressure drop across the spring-loaded check valve 13is suflicient to open the valve. The flow of cold water through thevalve 13 into the storage tank 9 permits hot water to flow out of thetank through the line 12 and thus augment the flow of hot water into thesupply line 10. The circulating pump 15, sensing cool water adjacent thecirculating line 14, will operate to short-circuit cold water back tothe branch line 6 to the heater, but by limiting this How to about 10%of that through the line 8 this short-circuiting has little effect onthe ability of the storage tank to supply hot water to the demand line10. When the hot water demand does not exceed the capacity of the heaterand the spring-loaded check valve 13 is closed, the circulating pumpdraws water from the storage tank through the by-pass line '14 anddelivers it through the cold water branch line 6 to the heater. The flowof water from the storage tank into the circulating line 14 causes hotwater to flow into the storage tank through the hot water branch line 12so that there is established a circulating How of water from the storagetank to the heater and back to the storage tank until the temperature ofthe water leaving the tank is high enough to actuate the sensor 17 andshut off the circulating pump 15. In this way, the system operates tobuild up a full supply of hot water in the storage tank whenever thestorage tank supply is not being used to meet a peak demand exceedingthe heater capacity.

The operation of the system shown in FIG. 2 is essentially the same asthat in FIG. 1. However, the variable flow rate valve 31 is closedwhenever the hot water demand is at a peak so that the short-circuitedWater from the storage tank to the cold water branch line 8 is limitedto that which can pass through the relatively low fixed flow-rateorifice 30. Whenever the hot water demand does not exceed the heatercapacity, the signal supplied by the generating device 26 will beinsufiicient to hold the valve 31 fully closed and this will permit thevalve 31 to permit a higher rate of flow of water from the storage tankto the heater and back to the storage tank through the hot water branchline 12. As in the system shown in FIG. 1, this permits the hot watersupply in the storage tank to be built up whenever the hot water demandis within the capacity of the heater to supply. As a consequence, thestorage tank is ready to supply hot water at peak demand rates. at morefrequent intervals than has been possible with prior art hot waterheating systems.

We claim:

1. In a hot water supply system including a hot water heater, a hotWater storage tank, a cold water supply line having a branch linecommunicating with the heater and another branch line communicating withthe storage tank, and a hot water supply line having a branch linecommunicating with the heater and another branch line cornmunicatingwith the storage tank, the improvement which comprises a spring-loadedcheck valve positioned in the cold water branch line to the storage tankand operable to permit flow therethrough to the tank when the pressurein the tank is reduced by the demand to a level representative of themaximum heating capacity flow rate of the heater, and a by-passreverse-flow circuit connected across the spring-loaded check valve insaid cold water branch line, the by-pass circuit including a circulatingpump operable in response to a water temperature in the storage tankbelow a predetermined storage temperature and a check valve disposed topermit flow from the pump through the by-pass line only in a directionopposite to the direction of flow of cold water through the springloadedcheck valve.

2. A hot water supply system according to claim 1 in which the by-passreverse-flow circuit includes a two-line parallel flow circuitpositioned in the bypass line with a fixed flow-rate valve in one linethereof and with a controlable flow rate valve in the other linethereof, and a control element for said controllable flow rate valveresponsive to a pressure drop in the hot water supply line and adaptedto close the valve when there is no demand on the hot Water supply line.

3. A hot water supply system according to claim 1 in which the two-lineparallel flow circuit is integrally formed in a single valve having afixed-flow rate orifice and a controllable flow rate valve connected inparallel.

References Cited UNITED STATES PATENTS 2,399,985 5/1946 Chandler 126362X 3,007,470 11/1961 Heeger 126-362 KENNETH W. SPRAGUE, Primary Examiner.

1. IN A HOT WATER SUPPLY SYSTEM INCLUDING A HOT WATER HEATER, A HOTWATER STORAGE TANK, A COLD WATER SUPPLY LINE HAVING A BRANCH LINECOMMUNICATING WITH THE HEATER AND ANOTHER BRANCH LINE COMMUNICATING WITHTHE STORAGE TANK, AND A HOT WATER SUPPLY LINE HAVING A BRANCH LINECOMMUNICATING WITH THE HEATER AND ANOTHER BRANCH LINE COMMUNICATING WITHTHE STORAGE TANK, THE IMPROVEMENT WHICH COMPRISES A SPRING-LOADED CHECKVALVE POSITIONED IN THE COLD WATER BRANCH LINE TO THE STORAGE TANK ANDOPERABLE TO PERMIT FLOW THERETHROUGH TO THE TANK WHEN THE PRESSURE INTHE TANK IS REDUCED BY THE DEMAND TO A LEVEL REPRESENTATIVE OF THEMAXIMUM HEATING CAPACITY FLOW RATE OF THE HEATER, AND A BY-PASSREVERSE-FLOW CIRCUIT CONNECTED ACROSS THE SPRING-LOADED CHECK VALVE INSAID COLD WATER BRANCH LINE, THE BY-PASS CIRCUIT INCLUDING A CIRCULATINGPUMP OPERABLE IN RESPONSE TO A WATER TEMPERATURE IN THE STORAGE TANKBELOW A PREDETERMINED STORAGE TEMPERATURE AND A CHECK VALVE DISPOSED TOPERMIT FLOW FROM THE PUMP THROUGH THE BY-PASS LINE ONLY IN A DIRECTIONOPPOSITE TO THE DIRECTION OF FLOW OF COLD WATER THROUGH THE SPRINGLOADEDCHECK VALVE.